Degumming gasoline and the like



Aprifl 28,1936. D. R. STEVENS ET AL DEGUMMING GASOLINE AND THE LIKEFiled May 5. 1930 Elmo/MM DonaZcLR.STe@ems,

' Willa Lean my W Patented Apr. 28, 1936 UNITED STATES PATENT OFFICEGruse, Wilkinsburg, Pa., assignors,

by mesne assignments, to Gulf Oil Corporation of Pennsylvania,Pennsylvania Pittsburgh, Pa., a corporation of Application May 3, 1930,Serial No. 449,680 10 Claims. (01. 196-93) This invention relates todegumming gasoline and the like; and it comprises a process wherein abody of liquid gasoline or analogous oil is heated under pressure to atemperature not less than about 700 F. for a period not greater than 30minutes, the pressure being usually of the order of about 1000 poundsper square inch and being either that developed by heating or by pumppressure, or both; all as more fully hereinafter set forth and asclaimed.

In theuse of gasoline from cracking plants an annoying feature is thedevelopment of gum on storage. The gasoline as first made contains noactual gum but it does contain bodies which in time, that is in storageor on standing, tend to develop gum; this tendency being aided by thepresence of oxygen, that is, by contact with air. It is not practicableto free the gasoline of gum by redistillation. The nature of the gum orof the bodies which yield it is not known, but it is supposed that thegum is formed by the polymerization of diolefins or some otherunsaturated bodies, probably assisted by oxidation. Whatever theseunsaturated bodies are, they are of the general physical type ofgasoline and are useful components of the mixture, provided they do notpolymerize to form gum.

We have found that by heating gasoline distillates under pressure for alimited time in the absence of catalysts and of added hydrogen to atemperature considerably in excess of the normal vaporizingtemperature,but below a temperature suificiently high to recrack suchdistillates. The so treated gasoline upon redistillation is found to bepermanently substantially free of gum and of the tendency to develop gumon standing. Our invention contemplates treatment of hydrocarbondistillate for a period of time up to fifteen minutes, while maintainingsaid distillate under a pressure of about one thousand pounds per squareinch. This result may be due either to the rearranging of thegum-forming hydrocarbons into more stable forms, or it may be due to therapid completion of the polymerizing action, thus removing gum andpotential gum. There is danger, however, in this reheating, of thepolymerization going too far and forming high- .boiling oils fromlow-boiling oils; this is particutimes of heating are employed, say atmoderate temperature. There is further a danger in the oppositedirection, in that cracking may occur with the development of gases andsome coke from the gasoline. This is particularly true at hightemperatures, Both these diificulties should be avoided.

larly true when long We have found that by heating gasoline distillatesto a temperature of about 750 F. and holding them under high pressure atthis point for about minutes there is substantially no loss in gasolineby cracking and the gasoline is freed of gum and of tendency to developgum on standing. In the case of gasoline distillates from liquid phasecracking, the optimum temperature seems to be about 790 F. while thedangerous temperature is about 40 degrees higher or 830 F. With gasolinedistillates made by a vapor phase operation, the optimum temperature ofheating is somewhat lower, being about 770 F. with a danger range againabout 40 degrees higher, say, about 810 gasoline and the like materialscommercially used, such as the drips from a gas plant handling crackingstill gases, at lower limit may be used; about 735 F. For this type ofmaterial the dangerous temperature is about 60 degrees higher. Inconsidering the time necessary to effect substantial improvement of thedistillate, a distinction must be drawn between preformed gum, thatexisting in the distillate and remaining after evaporation in an inertatmosphere such as steam, and potential gum, that to be expected afterthe gasoline has been exposed to oxidation in storage for a prolongedperiod. This potential gum is determined by a combination of oxidationand evaporation as in the copper dish test or the oxygen gum method ofVoorhees and Eisinger, Journal of the Society of Automotive Engineers,25, 584 (1929). We have found that the preformed gum may be removed veryeasily; that is, by a short time of exposure to temperatures of the sameorder as those mentioned above as effective. Even lower temperature maybe used. For example, the preformed gum in a liquid phase crackedgasoline was lowered from 37.4.- mg./ co. to 2.6 mg./100 cc. by exposureto a temperature of 660 F. at 500 pounds pressure for six minutes. In avapor phase cracked gasoline the preformed gum was lowered from 200 mg./100 cc. to 6.4 mg./100 cc. by exposure to 660 F. at 500 pounds for sixminutes. The potential gum is not sufficiently lowered under theseconditions and it is necessary to prolong the time and adjust thetemperature as indicated in the preceding paragraph. Conditions suitablefor removing potential gum will also remove preformed gum.

By working within the temperature limits indicated, gum and the gumyielding tendency are positively obviated while the losses bypolymerization and by cracking are minimized. In other words, byoperating within the temperature limits F. With some highly unsaturatedI specified the amount of actual gasoline left after treating closelycorresponds to the amount of gasoline treated, while gum and gumyielding compounds are obviated. By working at either a higher range oftemperature or a lower range of temperature neither result is positivelysecured. Within the desirable limits, however, the higher thetemperature, the less is the time necessary.

We have found portions of gasoline distillates boiling in differenttemperature ranges may advantageously be treated under somewhatdifferent conditions. For instance, the higher boiling portion of acracked gasoline distillate (that boiling above 280 F.) may be treatedat 790 F., and the lower boiling portion (that boiling below 280 F.) at750 F., each for 30 minutes under pressure. The treated fractions whenmixed, and the resulting gasoline distilled out, yielded a productbetter as to gum properties than when the whole distillate was treatedall at once.

As to the optimum pressure for treatment we have observed that improvedgum reduction is obtained as the pressure is raised to about 1000- 1200pounds, but that above this pressure no substantial further benefit isobtained.

There is some advantage in condensing the reheated material underpressure, this being presumably equivalent to slight extension in timeof treating.

In operating under the described invention, any convenient type ofapparatus may be employed. With batch operation, autoclaves, boilers andthe like may be employed, while in continuous operation liquids to betreated may travel in countercurrent to liquid which has undergonetreatment, thereby economizing heat. The particular nature of theapparatus forms no part of the present invention.

Our invention may be described by reference to the accompanying drawingwhich shows, more or less diagrammatically, an organization of apparatuselements useful for carrying out our process. In this showing:

Fig. 1 is a diagrammatic, elevational view, partly in section, of thecomplete apparatus required for the conduct of our process, while Fig. 2is a similar view of the apparatus required in a modification of thelater steps of our process.

In the figures like apparatus elements are designated by like referencenumerals.

Referring to Fig. 1, element l is a tank acting as a source of supplyand containing gasoline distillate from a cracking process, or it may bea tank of finished gasoline which is to be re-treated to reduce itstendency to form and deposit gum. The material to be treated inaccordance with my invention is withdrawn from tank I through line 2. Itpasses through a pump 3 which forces it through line 4 into heating coil5, this coil being situated in furnace 26. In coil 5 the gasoline isheated to a high temperature, usually from 700 to 800 F., under apressure which may be of the order of 1000 pounds per square inch. It isheld under these temperatures and pressures for a period of time usuallyless than 30 minutes. After the necessary treatment at high temperatureand under high pressure in coil 5, the material may be conveyed throughlines 6 and 1 to a condenser 8. Otherwise the heat treatment may beprolonged by passing the hot material from coil 5, through the chamberl9; as described subsequently, prior to condensation. The condensedmaterial fiows through line 9 into iractionator l0 and that sometimesthe different.

in this fractionator the desired constituents, having boiling pointswithin the gasoline range, are separated from high boiling pointpolymerization products and any other high boiling point constituentswhich leave the fractionator by line 13. The vapors within the gasolinerange leave the fractionator through line I2. The necessary heat for thefractionation may be supplied by a steam coil II in the base of thefractionator. The vapors in line l2 pass to a condenser l3, where theyare liquefied, and from there pass through line id to a separator l5.The desired stabilized gasoline is withdrawn from separator l5 throughline l6, any uncondensed gas is withdrawn from the separator throughline I1, and condensed steam is withdrawn from the separator throughline l8.

if the time of passage of vapors through coil 5, after attaining thedesired temperature, is insufficient to accomplish the desired gumstabilization, the vapors from coil 5 are passed through a largecapacity chamber l9 prior to condenser B. Valves are provided on thelines to permit routing the vapors either through line 6 or chamber l9.

Fig. 2 illustrates a later steps in the process of Fig. l and permits aconsiderable saving in heat as tion in the necessary amounts of steamand cooling water. In this modification the coil 8 is operated as acooling coil rather than as a total condenser, and at that point thevapors are cooled only to the point necessary to obtain properfractionation in fractionator Illa. The so cooled stream is deliveredthrough line 9 to a separator 22, where the liquid constituents areseparated from the vapor constituents. These two streams are thendischarged through lines 23 and 24, respectively, into fractionator "la,the liquid constituents being introduced into the i'ractionator at ahigher point than are the vapor constituents.

Gum is highly undesirable in motor fuels, tending to increase carbondeposits, forming gummy deposits on the valves, and in fold, as well aspossibly interfering with carburetion. It is therefore highly desirablenot only to remove any gum present in gasoline but to treat it so thatgum will not form. However, distillates from which gasoline isfractionated may be treated in accordance with our invention-pressurestil distillates, vapor phase distillates and the like, with, not onlyimprovement in such distillates, but with improvement in differentfractions obtainable therefrom including gasoline. It is thereforewithin the purview of our invention to treat such distillates aspressure still distillate, vapor phase distillate, or in fact anydistillate containing gum or of a char-* acter likely to form gum aswell as to treat gasoline itself.

By the terms cracked gasoline and cracked gasoline distillate employedin the claims we mean a gasoline or a gasoline distillate produced bythe cracking of a heavier oil.

What we claim is:

1. In a process of degumming cracked hydrocarbon distillate by simpleheat and pressure treatment, the step which comprises heating such adistillate in the absence of catalysts and of added hydrogen to atemperature between 700 and 800 F. for about 6 to 30 minutes whilemaintaining said distillate under a pressure of about 1000 pounds persquare inch, the said cracked the intake manidistillate being of suchtype as to show substan tially no cracking under the conditions stated.

2. In a process of degumming cracked gasoline distillates by simple heatand pressure treatment, the step which comprises heating such adistillate in the absence'of catalysts and of added hydrogen to atemperature between about 700 and 800 F. for a period sufiicient toeffect degumming of the material under treatment but not substantiallylonger than 30 minutes while maintaining such distillate under apressure of about 1000 pounds per square inch.

3. In a process of degumming cracked hydro-- carbon distillates bysimple heat and pressure treatment, the step which comprises heatingsuch a distillate in the absence of catalysts and of added hydrogen to atemperature of about 750 F. for a period of time suflicient to efiectdegumming but not substantially exceeding 30 minutes, while maintainingsaid distillate under a pressure of about 1000 to 1200 pounds per squareinch; the said cracked distillates being of such type as to showsubstantially no cracking under the conditions stated.

4. In a process of degumming cracked gasoline distillates by simple heatand pressure treatment, the step which comprises heating such adistillate in the absence of catalysts and of added hydrogen to atemperature above 700 F. but not sufiiciently high to re-crack it, for aperiod of time suflicient to effect degumming but less than 30 minutes,while maintaining said cracked distillate under pressure Within therange of about 1000 to 1200 pounds per square inch.

5. In the process of degumming cracked gasoline distillates by simpleheat and pressure treatment, the process which comprises dividing acracked gasoline distillate into two fractions, one having a higherboiling range than the other, heating said fractions separately in theabsence of catalysts and of added hydrogen to temperatures between about700 and 800 F. under pressures of the order of 1000 to 1200 pounds andfor a period of from about 6 to 30 minutes, the higher boiling of thesaid two fractions being heated to a temperature approximately 40 F.higher than that to which the said lower boiling fraction is heated, anduniting the so-treated fractions.

6. In a process of degumming cracked hydrocarbon distillates by simpleheat and pressure treatment, the step which comprises heating such adistillate in the absence of catalysts and of added hydrogen to atemperature between about 700 and 800 F. under pressures of the order ofabout 1000 to 1200 pounds for a period of time not substantiallyexceeding 30 minutes but suflicient to efiect degumming, the saidcracked distillate being of such type as to show substantially nocracking under the conditions stated.

7. In a process of degumming cracked hydrocarbon distillates by simpleheat and pressure treatment, the process which comprises heating such adistillate under pressures of the order of 1000 to 1200 pounds in theabsence of catalysts and of added hydrogen to temperatures above 700 F.but insuflicient to cause substantial cracking, for a period of timeranging from about 6 to 30 minutes.

8. In a process of degumming cracked hydrocarbon distillate by simpleheat and pressure treatment, the step which comprises heating such adistillate in the absence of catalysts and of added hydrogen to atemperature considerably in excess of the normal vaporizing temperature,but below a temperature sufiiciently high to recrack such distillate,for a period of time not in excess of 30 minutes, while maintaining saiddistillate under a pressure of about 1000 pounds per square inch.

9. The process of claim 7 wherein agasoline distillate from a liquidphase cracking process is employed and the heating temperature is of theorder of 790 F.

10. The process of claim 7 wherein said gasoline distillate is from avapor phase cracking operation and the heating temperature is of theorder of 770 F.

DONALD R. STEVENS. WILLIAM A. GRUSE.

